Back pressure regulators have been commercially available for decades. As the name implies, they regulate back pressure in a fluid system and are commonly used to serve as a relief valve or constant spill off device to limit excess pressure to a desired operating pressure range. For example, FIG. 1 shows a system 100 that includes a back pressure regulator 102 having an inlet 103 and an outlet 105. The regulator 102 reduces pressure by delivering fluid from the inlet 103 to a supply reservoir 106 at the outlet 105. The outlet 105 is typically at atmospheric pressure, while the inlet 103 is at an elevated pressure. A significant drawback in conventional back pressure regulators is cavitation conditions that can occur when there is a large pressure differential (e.g., 1,000 pounds per square inch (psi)) between the inlet 103 and the outlet 105. Cavitation conditions occur when fluid velocities are fast enough to cause the pressure at the velocity point to drop below the vapor pressure of the liquid. When pressure in the liquid drops below the liquid vapor pressure it creates a collapsing bubble and the pressure is recovered downstream of the choking point where the fluid slows down. This collapsing bubble can cause a point pressure load of up to approximately 300,000 psi on valve surfaces. This high contact pressure also causes an instantaneous heating at the collapsing bubble. The high heat and high contact pressure can erode the throttle surface.
High pressure differential can also cause other problems, such as high frequency flow noises that reverberate throughout a piping system. These noises can be extremely loud and may, in some cases, require installing noise suppression systems to meet safety standards. Another problem with conventional back pressure regulators is that the can include internal components that work against one another. For example, U.S. Patent Application No. US2010/0206401 discloses a two stage device with the second stage governing the pressure drop across the first stage. The second stage balances two different pressures inside the regulator against the pressure outside of the regulator over a bound area to create a force that governs the pressure differential across the first stage. A spring governs the pressure drop across the stage upstream of it. Flow passes through the second stage by going around a throttling pin then through the throttling seat. In this arrangement, a spike in inlet pressure will cause the second stage piston to drive towards the seat causing unstable pressure regulation. When two or more of these devices are installed in parallel, they can fight each other without external pressure spikes causing this effect. Accordingly, there is a need for back pressure regulators that can operate under high pressure differentials without causing cavitation and excessive reverberation.